ComputeLagrangianStrain

Compute strain in Cartesian coordinates.

Overview

The ComputeLagrangianStrain class calculates the basic kinematic quantities used by the new mechanics kernels mechanics kernels. The theory section on the new material system describes this class's role in greater detail, the following gives a brief description.

The class calculates the strain measures available for the constitutive models to use to define the stress update and the kinematic tenors required to setup the stress equilibrium problem for large deformation simulations. The stabilize_strain averages the volumetric/dilatational part of these strain measures using an stabilization approach to prevent locking of linear quad and hex elements for problems experiencing incompressible deformation. This class also adds in the extra deformation gradient imposed by the homogenization system.

The calculations differ somewhat between small and large deformation kinematic theory. The large_kinematics flag selects between the two theories. This flag should be consistent between the strain calculator and the kernels. The stabilize_strain flag determines if the calculator uses the stabilization Souza Neto et al. (1996).

Step-by-step the class:

  1. Calculates the deformation gradient as for large deformations or for small deformations.

  2. If stabilize_strain is set, average the volumetric parts of the deformation gradient, as described in the stabilization documentation.

  3. If active, add the extra gradient to this displacement-based deformation gradient calculated in the ComputeLagrangianHomogenizedLagrangianStrain.

  4. For large deformations only, calculate the kinematic tensors used to define the equilibrium problem in the right frame of reference in the kernels. For small deformations these measures are set to the identity.

  5. Calculate the increment in the spatial velocity gradient: for large deformations and for small deformations.

  6. Calculate the total strain increment as .

  7. Sum up and subtract the eigenstrain increment over the step to fine the mechanical strain increment, .

  8. Use the previous step values of total and mechanical strain to calculate the updated strain values: and .

commentnote

The strain calculator does not apply the eigenstrains to the deformation gradient, only the incremental and integrated strain measures.

schooltip

stabilize_strain should be set to true for problems using linear quad or hex elements where the material model produces incompressible or near-incompressible deformation. It should be set to false for higher order elements. The stabilization is ineffective for linear triangle or tet elements and these elements should not be used for incompressible or near-incompressible problems.

The calculator requires use_displaced_mesh=false and enforces this with an error.

Example Input File Syntax

The following example sets up the ComputeLagrangianStrain object for a large deformation problem without stabilization. For small deformations the only change would be large_kinematics=false.

[Materials]
  [elastic_tensor]
    type = ComputeIsotropicElasticityTensor
    youngs_modulus = 1000.0
    poissons_ratio = 0.25
  []
  [compute_stress]
    type = ComputeLagrangianLinearElasticStress
    large_kinematics = true
  []
  [compute_strain]
    type = ComputeLagrangianStrain
    displacements = 'disp_x disp_y disp_z'
    large_kinematics = true
  []
[]
(moose/modules/solid_mechanics/test/tests/lagrangian/cartesian/updated/patch/large_patch.i)

Input Parameters

  • displacementsDisplacement variables

    C++ Type:std::vector<VariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:Displacement variables

Required Parameters

  • base_nameMaterial property base name

    C++ Type:std::string

    Unit:(no unit assumed)

    Controllable:No

    Description:Material property base name

  • blockThe list of blocks (ids or names) that this object will be applied

    C++ Type:std::vector<SubdomainName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The list of blocks (ids or names) that this object will be applied

  • boundaryThe list of boundaries (ids or names) from the mesh where this object applies

    C++ Type:std::vector<BoundaryName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The list of boundaries (ids or names) from the mesh where this object applies

  • computeTrueWhen false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.

    Default:True

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:When false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.

  • constant_onNONEWhen ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

    Default:NONE

    C++ Type:MooseEnum

    Unit:(no unit assumed)

    Options:NONE, ELEMENT, SUBDOMAIN

    Controllable:No

    Description:When ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

  • declare_suffixAn optional suffix parameter that can be appended to any declared properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Unit:(no unit assumed)

    Controllable:No

    Description:An optional suffix parameter that can be appended to any declared properties. The suffix will be prepended with a '_' character.

  • eigenstrain_namesList of eigenstrains to account for

    C++ Type:std::vector<MaterialPropertyName>

    Unit:(no unit assumed)

    Controllable:No

    Description:List of eigenstrains to account for

  • homogenization_gradient_namesList of homogenization gradients to add to the displacement gradient

    C++ Type:std::vector<MaterialPropertyName>

    Unit:(no unit assumed)

    Controllable:No

    Description:List of homogenization gradients to add to the displacement gradient

  • large_kinematicsFalseUse large displacement kinematics in the kernel.

    Default:False

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:Use large displacement kinematics in the kernel.

  • prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Unit:(no unit assumed)

    Controllable:No

    Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

  • stabilize_strainFalseAverage the volumetric strains

    Default:False

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:Average the volumetric strains

  • use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

    Default:False

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Optional Parameters

  • control_tagsAdds user-defined labels for accessing object parameters via control logic.

    C++ Type:std::vector<std::string>

    Unit:(no unit assumed)

    Controllable:No

    Description:Adds user-defined labels for accessing object parameters via control logic.

  • enableTrueSet the enabled status of the MooseObject.

    Default:True

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:Yes

    Description:Set the enabled status of the MooseObject.

  • implicitTrueDetermines whether this object is calculated using an implicit or explicit form

    Default:True

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:Determines whether this object is calculated using an implicit or explicit form

  • seed0The seed for the master random number generator

    Default:0

    C++ Type:unsigned int

    Unit:(no unit assumed)

    Controllable:No

    Description:The seed for the master random number generator

Advanced Parameters

  • output_propertiesList of material properties, from this material, to output (outputs must also be defined to an output type)

    C++ Type:std::vector<std::string>

    Unit:(no unit assumed)

    Controllable:No

    Description:List of material properties, from this material, to output (outputs must also be defined to an output type)

  • outputsnone Vector of output names where you would like to restrict the output of variables(s) associated with this object

    Default:none

    C++ Type:std::vector<OutputName>

    Unit:(no unit assumed)

    Controllable:No

    Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object

Outputs Parameters

References

  1. EA de Souza Neto, D Perić, M Dutko, and DRJ Owen. Design of simple low order finite elements for large strain analysis of nearly incompressible solids. International Journal of Solids and Structures, 33(20-22):3277–3296, 1996.[BibTeX]